TITLE:   Palmer LTER: environmental variability and the reproductive cycle of
         Antarctic Krill
AUTHORS: Langdon B. Quetin, Robin M. Ross
DATE:    2-4 August 2000
PLACE:   LTER All Scientists Meeting 2000, Long-Term Ecological Research:
	 Unifying Principles & Global Applications, Snowbird, Utah
         
	 University of California, Santa Barbara, CA 93106
	 Poster - Session: Population Studies/Biodiversity (W57)

ABSTRACT
Since the austral summer of 1993 the Palmer LTER has documented variation in
the reproductive cycle of Antarctic krill, <italic>Euphausia superba</italic>,
the key herbivore in the marine pelagic ecosystem.  Interannual variation in 
timing of reproduction, the percent of females reproducing, and number and size
of eggs produced is significant.  Distribution and abundance of a
possible competitor, the salp (<italic>Salpa thompsoni</italic>), also
showed large variations.  Reproductive variation in krill is assumed to
stem from food-limitation, with food necessary both in the spring for
ovarian maturation, and in the summer for oocyte maturation.  Two
scenarios have been proposed to explain this variation.  One
hypothesizes that early sea ice retreat leads to abundant salp
populations, and salps out-compete krill populations for limited food
resources.  The alternative proposes that differences in the timing and
extent of sea ice lead to variation in the availability of
ice-associated food resources.  In either case, interannual variability
in the krill reproductive cycle is correlated with sea ice.  The seven
year time series of the Palmer LTER allows us to examine the effects of
spring sea ice dynamics, annual primary production, and salp abundance
on reproductive success in Antarctic krill, and to differentiate
between the above scenarios<fontfamily><param>Times</param>.